And it is not only businesses deliberately exploiting their workers that are affected. Companies can be tainted by slavery because of practices in their supply chains and/or supplier networks offshore, as Nestlé and other companies discovered in 2015 when it came to light that they had been sourcing fish products from Thailand which had been caught and processed by slave labour.
Kevin Hyland, the UK's Independent Anti-Slavery Commissioner, has observed, "Slavery exists in the supply chains of legitimate businesses".
New Zealand risks falling behind countries we like to compare ourselves to, such as Australia and the UK, in our response to modern slavery, both at home and in the supply chains of businesses operating here.
In Australia, migrant exploitation and modern slavery have been much in the headlines lately. The convenience store franchise chain 7-Eleven recently compensated over 2800 workers for wage theft in excess of A$110 million ($115m). Domino Pizza franchisees in Australia have also faced accusations of wage theft. In the agricultural sector, exploitative conditions for migrant workers have come to light, with one worker receiving as little as A$150 for six months work.
Longstanding Australian criminal laws against trafficking and slavery have not prevented these crimes happening, and, for the most part, have not been relied on by authorities to prosecute exploitation.
Queensland is introducing a licensing scheme for labour hire companies that includes penalties and makes offenders liable to criminal prosecution. The Australian Federal Government has recently launched an inquiry into establishing a modern slavery act.
Now it's our turn. Last year, we released findings from a two-year research project, "Worker exploitation in New Zealand: A troubling landscape", which left no room for doubt that modern slavery is a pressing issue here, too.
We called for, among other things, a human trafficking office to co-ordinate a response to human trafficking and labour exploitation, a review of the current law to see if it allows for effective prosecution of human trafficking, and a review of the UK Modern Slavery Act 2015 and similar international laws to determine whether New Zealand should legislate to make it unlawful for companies with slavery in their supply chain to operate in New Zealand.
We commend the Government's introduction of a ban on hiring migrants for bosses caught exploiting migrant workers, but we need to go much further.
The UK Modern Slavery Act has seven parts, including protection for victims, civil and criminal provisions, new maritime enforcement mechanisms, and the establishment of an anti-slavery commissioner. Crucially, it compels companies to take responsibility for tackling slavery in their supply chains.
There is evidence the act is already driving change in corporate behavior, as companies with turnover of £36m ($63m) or more are obliged to disclose annually what they are doing to ensure transparency in their supply chains.
Another example is the California Transparency in Supply Chains Act. Both laws recognise that companies cannot solve this problem on their own.
We challenge the Government to take the necessary steps now to consider a modern slavery act here. New Zealand must clearly legislate that slavery in any corporate supply chain or local business will not be tolerated.